Brevidens Birindelli, Sidlauskas & Melo, 2025

Sidlauskas, Brian L., Melo, Bruno F., Birindelli, José L. O., Burns, Michael D., Frable, Benjamin W., Hoekzema, Kendra, Dillman, Casey B., Sabaj, Mark H. & Oliveira, Claudio, 2025, Molecular phylogenetics, a new classification, and a new genus of the Neotropical fish family Anostomidae (Teleostei: Characiformes), Neotropical Ichthyology (e 240076) 23 (1) : -

Brevidens Birindelli, Sidlauskas & Melo , new genus urn:lsid:zoobank.org:act:7AF3926D-074D-41D9-8406-28D124AB554D

Type-species. Leporinus striatus Kner, 1858:79 , herein designated.

Diagnosis. Brevidens differs from all other members of Anostomidae by possessing a fourth dentary tooth that is distinctly smaller than the anterior three teeth and separated from those teeth by a diastema ( Fig. 2). Brevidens is further diagnosed by the following non-exclusive morphological features: four dark longitudinal stripes on the body; three premaxillary teeth; 16 scale rows around the caudal peduncle; a red spot on the ventral portion of the upper lip in life; subterminal mouth, its cleft longitudinally aligned with the ventral border of the eye in 60 mm SL or larger specimens.

Comparisons. Externally, Brevidens striatus can be quickly distinguished from all anostomids, except Anostomus anostomus , A. ternetzi Fernández-Yépez, 1949 , Hypomasticus arcus (Eigenmann, 1912) , H. despaxi (Puyo, 1943) , H. tepui (Birindelli, Britski & Provenzano, 2019) , Leporinus sexstriatus Britski & Garavello, 1980 , L. tristriatus Birindelli & Britski, 2013 , and Petulanos brevior (Géry, 1961) (new combination, see below), by having more than two dark longitudinal stripes on the body. Brevidens striatus is distinguished from all species of Anostominae by having a subterminal mouth (vs. superior), three premaxillary teeth (vs. four), and unicuspid incisiform teeth (vs. multicuspid crenate teeth). Brevidens is distinguished from Hypomasticus arcus , H. despaxi , and H. tepui by having three teeth on the premaxilla (vs. four), the dark midlateral stripe on the body continuous with a dark stripe on the head (vs. discontinuous), and the ventralmost stripe on the body not continuing anteriorly onto the head (vs. continuing). Brevidens is distinguished from L. tristriatus and L. sexstriatus by having four dark stripes on the body (vs. three or six), 16 scale rows around the caudal peduncle (vs. 12), a red spot on the ventral portion of the upper lip in life (vs. absent) and a subterminal mouth with its cleft longitudinally aligned with the ventral border of the eye in 60 mm SL or longer specimens (vs. a subinferior mouth with a cleft aligned with the ventral border of the infraorbitals).

Etymology. From the Latin brevis, meaning short, plus the Latin dens, meaning tooth, in reference to the abbreviated fourth dentary tooth that diagnoses the genus. Gender masculine.

Geographical distribution. Brevidens has a large geographical distribution including cis- and trans-Andean rivers. On the eastern side of the Andes, it occurs in the Uruguay, Paraná and Paraguay basins of Argentina, Bolivia, Brazil, and Paraguay, in the western Amazon basin of Brazil, Bolivia, Colombia, Ecuador, and Peru, and in the Orinoco basin of Colombia and Venezuela. Its trans-Andean distribution includes the Atrato, Magdalena, and Sinú rivers of Colombia (Birindelli, Britski, 2013).

Diversity. Birindelli, Britski (2013) found no obvious external morphological characteristics that would subdivide Brevidens striatus into multiple species. Nevertheless, its widespread geographical distribution includes areas that have been isolated from adjacent drainages for millions of years, such as the upper La Plata, Amazon, Orinoco, and the Magdalena basins (Lundberg et al., 1998; Albert, Reis, 2011; Aguilera et al., 2013). That occurrence in so many different river systems suggests that the diversity of Brevidens may be underestimated.

Monophyly, relationships and taxonomy of subfamilial lineages. Maximum likelihood ( Figs. 3, S 1) and Bayesian reconstructions ( Fig. S2) agreed unequivocally about the monophyly of Anostomidae , its three major subclades, and the relationships among them. Within Anostomidae , the initial split divides Leporellus Lütken, 1975

and the genera of Anostominae (sensu Winterbottom, 1980) from the remainder of the family ( Fig. 3). Each of these lineages received full statistical support (100% bootstrap; 1.0 posterior probability) and have been recovered consistently in prior phylogenetic studies incorporating molecular data (Ramirez et al., 2017b; Betancur-R. et al., 2019; Sidlauskas et al., 2021; Melo et al., 2022). As such, we elevate the three major lineages to subfamilial status, using names established in prior literature. We refer Leporellus to Leporellinae Eigenmann, 1910 ( Fig. 3), Anostomus , Gnathodolus , Petulanos , Pseudanos , Sartor and Synaptolaemus to Anostominae Günther, 1864 , and Abramites , Anostomoides , Brevidens , Hypomasticus , Insperanos , Laemolyta , Leporinus , Megaleporinus , Rhytiodus , and Schizodon to Leporininae Eigenmann, 1912 ( Fig. 3). The inclusion of Insperanos in Leporininae is based on the results of Sidlauskas et al. (2021) which placed Insperanos as the sister lineage to the remainder of that subfamily with 86% posterior probability.

Though the family group name for Anostominae comes from Anostomatina of Günther, 1864, the first usage of Anostominae (with that spelling) appears to be that of Myers (1950). His subfamilial concept matches that of the whole family Anostomidae as treated herein, as does Günther’s (1864) Anostomatina. Our concept of subfamily Anostominae more closely matches that of Winterbottom (1980).

Though our classification for Anostomidae uses Linnean-rank subfamilies, we also provide definitions that adhere to PhyloCode (Queiroz, 2006; Queiroz, Cantino, 2020; Laurin, 2023), a rank-free system of classification that has gained substantial current traction and that uses explicit patterns of common ancestry and apomorphy to define taxa. In so doing, we erect a framework compatible with the two major classifications of actinopterygian fishes currently being debated by the ichthyological community (Betancur-R. et al., 2013; Near, Thacker, 2024)